[BUG]: TemplateModel.substitute_parameter does not substitute parameter used in initial expressions

[liunelson]

This method should also check the initial expressions:

mira/mira/metamodel/template_model.py

Line 1023 in d42e7e9

def substitute_parameter(self, name, value=None):

Proposal:

        for template in self.templates:
            template.substitute_parameter(name, value)
        for observable in self.observables.values():
            observable.substitute_parameter(name, value)
        for initial in self.initials.values():
            initial.substitute_parameter(name, value)